Anti-ring-sticking lubricant



Patented June 1, 1943 ANTI-RING-STICKING LUBRICANT Ellis R. White,Albany, Calif., assignor to Shell Development Company, San Francisco,Calif., a corporation of Delaware No Drawing. Application January 13,1941, Serial No. 374,201

11 Claims.

This invention is related to improved lubricating oils, and moreparticularly deals with mineral lubricating oils containing dissolvedtherein small amounts of oil-soluble metal salts capable of reducingringsticking tendencies of the oil.

It is well known that in Diesel engines in particular, piston rings havea tendency to become stuck due to an accumulation of coke in the ringgrooves. It is also known that the addition of oil-soluble detergents tothe lubricating oil does in many instances reduce or even prevent suchringsticking. The class of detergents most active for this purpose areoil-soluble metal salts of carboxylic and sulfonic acids, such as soapsof fatty acids, chlorinated fatty acids, aromatic fatty acids,naphthenic acids, rosin acids, paraffin carboxylic acids (produced byoxidation of paraffin wax), mahogany acids, alkyl derivatives of benzoicor hydroxy benzoic acids and many others. Salts of polyvalent metals arein general most active, e. g., of Mg, Ca, Sr, Ba, Zn, Cd. Al, Sn, Sb,Cr, Mn, Co, Ni, etc.

The addition of oil-soluble salts to lubricating oils in effectiveamounts, e. g., in amounts ranging from about 25% to 5.0%, however,introduces at the same time a number of difficlllties, one of the mostserious of which is bearing corrosion. Another is formation of hardcoke. and still another is scratching of the top land of the piston.

The problem of corrosion seems to be very involved, corrosion apparentlyproceeding by at least one of several possible mechanisms with theeffect that under some conditions an oil coniaining adissolved salt maybe non-corrosive and even a corrosion preventive, whereas under otherconditions it may cause serious corrosion. Thus some oils containing adissolved salt are initially corrosive, while others are initiallynoncorrosive but acquire induced corrosiveness, i. e., turn corrosiveupon use under ordinary lubricating conditions as are encountered ininternal combustion engines. In some instances corrosion has beenreduced, though not usually altogether overcome, by the addition ofvarious secondary dopes, such as anti-oxidants, anti-corrosives, etc. Inthis connection, it should be observed that in some instances theaddition of secondary dopes has an effect contrary to what one shouldexpect, 1. e., cases are known in which, for example, a lubricating oilcontaining the combination of an oil-soluble salt and a provencommercial anti-corrosive are more corrosive than the same oilcontaining the salt alone.

Among the detergents most valuable for antiringsticking purposes are thealiphatic carboxylic acids, e. g., fatty acids, aromatic fatty acids,naphthenic acids, paraflln carboxyl acids, rosin acids, etc. However,they all suffer from the common disadvantage of relatively highcorrosiveness which may be initially active or be induced upon use.

It is a. purpose of this invention to produce relatively non-corrosivelubricating oils suitable for internal combustion engines containingdissolved a detergent soap. It is another purpose to produce improvedoil-soluble salts of aliphatic acids, which salts, when dissolved inmineral lubricating oils, combine an extraordinary degree of detergencywith but little corrosiveness.

I have discovered that the corrosiveness of oilsoluble salts ofaliphatic, alicyclic, aromatic carboxylic acids can be reducedmaterially and in many instances be suppressed to relatively harmlessproportions by attaching an amino radical onto the carbon atom in thealpha position to the carboxyl radical. Thus the acids suitable for mypurpose are amino acetic acid derivatives having the general formulaCOOK so des red. the R radicals may contain relatively propyl, butyl,amyl, hexyl, allyl, etc., primary or secondary amines, petroleum bases(particularly from straight run petroleum oils), piperidine,

Any of the metals heretofore known to be suitable for anti-ringstickingpurposes may be used. From the point of view of detergent eflect, thepolyvalent metals, Mg, Ca, Ba, Zn, Al, Sn, Cr and Co are preferred. Onthe other hand, salts of metals having a strong tendency to form complexcompounds, such as Cu, Ag, Ni, Co, Mn, Cr, etc., because of theirpreference to form chelates, are the least corrosive, as'will beexplained hereinafter. Either normal or basic salts or their mixturesmay be used.

As already stated. salts of the alpha amino acids are less corrosivethan the same salts of corresponding acids not containing the aminoradical, or containing an amino radical in a position other than thealpha position. While I do not wish to be bound by my theory, I believethat the following is explanation for the improved behavior. It appearsthat at least one of the mechanisms by which corrosion proceeds isdirectly related to the electrical conductivity of the oil. Mostoil-soluble salts, such as those heretofore used for impartingdetergency to lubricating oils are slightly ionized in hydrocarbon oilsolution, as a result of which the oil becomes conductive. However,salts of acids having a threevalent nitrogen in alpha position to thecarboxyl radical exist in two forms which are in equilibrium with eachother, namely, the chelate (inner ring) and the non-chelate forms. Thelatter ionizes, but the former does not. Thus the equilibrium may beillustrated as follows:

If a chelate form is the preferred one, relatively few ions can form,and the corrosion is accordingly reduced. Simultaneously, however, onewould expect a similar reduction in detergent properties, because, asfar as known, it is the ionized portion of the salt which is responsiblefor the detergent effect. However, the alpha amines do not show theexpected detergency loss, and, on the contrary, often are materiallybetter in this property than the same or similar salts of thecorresponding acids not having the alpha amino radical.

This is believed to be due to the fact that certain definite but smallamounts of ionized detergent salts displa y substantially as greatdispersive action as larger amounts, while the corrosive property ismore nearly proportional to the amounts of ions present. Thus, from thepoint of view of detergency of the oil, it is only necessary to have inthe oil at any one time the minimum amounts of active ions which arejust suiiicient to disperse whatever sludge or sludgelike materialshappen to be'contained in the oil at that moment. As the dispersionproceeds, these minimum amounts are used up and the oil would be leftunprotected, unless new active ions are introduced. Due to the presenceof relatively large amounts of inactive detergent salts, effectivequantities of these ions are quickly restored, and thus continueddetergency of the oil is assured.

Concerning the equilibrium between the chelate and the non-chelate formsof the normal and basic salts, it appears that in the case of the normalsalt the chelate is preferred, whereas in the basic salt the ionizedform predominates. As a result, it has been found that the normal saltsof the alpha amino acids are even less corrosive than the basic ones,whereas it was heretofore believed necessary that to suppresscorrosiveness one must employ the basic salts.

The above peculiar reversal of the rate of corrosiveness as affected byalkalinity in the case of the alpha amino salts is of considerableimportance. One of the main causes. for the type of corrosiveness whichis induced upon use of the oils containing detergent salts is believedto reside in a gradual reduction of the alkalinity of the salt with acommensurate decrease in the pH value due to oxidation. In the case ofthe alpha amino salts, however, the transition from the basic to thenormal salt has just the opposite effect, corrosion decreasing forreasons pointed out above, rather than increasing.

In the normal salts of some of the alpha amino acids the equilibrium infavor ofthe chelates is so pronounced that an amount of detergentactiveions may be formed less than the minimum required for truly satisfactorydetergency. In such cases it may be desirable to use a mixture of normaland basic salts so as to result in an oil solution containing therequired minimum amount of ions; or a mixture of a normal alpha aminocarboxylic acid salt with a detergent salt which is not subject tochelate formation, such as an ordinary oil-soluble naphthenate,sulfonate, aromatic fatty acid salt, paraiiln wax carboxylic acid salt,etc., may be employed.

a The following example serves to illustrate my invention: Stearic acidwas halogenated by the Hell Volhard Zelinsky reaction under conditionsto insure complete conversion of all the stearic acid to thecorresponding alpha halo acid halide. The resulting product washydrolyzed with warm water, and the halo acid thereby obtained was driedby solution in isopentane and subsequent crystallization. The alpha bromstearic acid, which had a melting point of 60 C., was then heated withtwo equivalents of piperidine for one The benzene layer was mixed withtwo equivalcnts of a thick freshly slacked lime paste and the mixturewas distilled with addition of more benzene until no further water cameoverhead with the benzene. When dry, the residual benzene solution wasfiltered to remove excess lime, and the filtrate was evaporated todryness.

The residue was a reddish yellow glassy substance which readilydissolved in hot oil.

A solution of 1.7% by weight oi this material in an SAE 30 minerallubricating oil was produced. The resulting blended lubricating oil wastested, and is compared in the table below with two recognized detergentsalts for Diesel lubricating oils for corrosiveness and detergency.

In the corrosion test a hardened steel disc is made to rotate for 20hours under constant pressure against 3 copper lead alloy bearings. Thebearing assembly rests in a welded steel cup and is covered with theo'ilto be tested. During the test the temperature of the oil ismaintained at 107 C. The bearings are weighed before and after the test,the difference in the weight representing the loss sustained during thetest.

The detergency is measured by filtering a suspension of carbon blackunder standard conditions through a column placed in a glass tube, whichcolumn consists of 1 cm. layers of a sand separated from each other bypieces of filter paper. As the oil filters through this column, thecarbon black is gradually filtered out and beginning at a certain pointdown the column, the oil is free from suspended carbon black. This pointcan readily be determined by visually examining the edges of the severalfilter papers. Those above this point have blackened edges, while thosebelow it remain white. By counting the number of blackened papers, adirect measure for the detergency is obtained. Under the conditions ofthe test straight lubricating oils have detergency numbers of 1-2. Thepresence of 1-2% of a good detergent normally raises it to 6-8, and inexceptional cases to 9 or 10.

In addition to the detergents of this invention, the lubricating oilsmay contain conventional oxidation inhibitors or retarders,anti-corrosives, extreme pressure agents, particularly those containingat least one of the elements S, Cl and P in relatively stable form, soas not to cause corrosion, blooming agents, dyes, etc. The amounts ofthe detergent required to retard or prevent ringsticking normally variesbetwen about 25% and and preferably from 175% to 2.5% by weight of theoil.

I claim as my invention:

1; Lubricating oil comprising mineral lubricating oil containingdissolved from .25%-5.0% of an oil-soluble polyvalent metal salt of analpha amino acetic acid which is resistant to oxidation under normallubricating conditions in internal combustion engines.

2. Lubricating oil comprising mineral lubricating oil containingdissolved a small amount of an oil-soluble salt combining a polyvalentmetal with an alpha amino acetic acid which is resistant to oxidationunder normal lubricating conditions in internal combustion engines.

3. Lubricating oil comprising a mineral lubricating oil containingdissolved a small amount of an oil-soluble polyvalent metal salt of analpha amino acetic acid which is resistant to oxidation under normallubricating conditions in internal combustion engines, the amino radicalof said acid being a secondary amino radical.

4. Lubricating oil comprising a mineral lubricating oil containingdissolved a small amount of an oil-soluble polyvalent salt of an alphaamino acetic acid which is resistant to oxidation under normallubricating conditions in internal combustion engines, the amino radicalof said acid being a tertiary amino radical.

5.'Lubricating oil comprising a mineral lubricating oil containingdissolved a small amount of an oil-soluble mixture of basic and normalpolyvalent metal salts of an alpha amino acetic acid which is resistantto oxidation under normal lubricating conditions in internal combustionengines.

6. Lubricating oil comprising a mineral lubricating oil containingdissolved a small amount 0! an oil-soluble mixture of a detergent saltnot subject to chelate formation and of a polyvalent metal salt of analpha amino acetic acid which is resistant to oxidation under normallubricating conditions in internal combustion engines.

7. Lubricating oil comprising a mineral lubricating oil containingdissolved from .25 to 5.0% of an oil-soluble polyvalent metal salt of amonocarboxylic acid having not more than one olefinic double bond andhaving the formula wherein R1 to R4 are hydrogen or hydrocarbonradicals, at least one being a hydrocarbon radical, the total number ofcarbon atoms in said radicals being at least 16 said salt being furthercharacterized by being resistant to oxidation under normal lubricatingconditions in internal combustion engines.

8. Lubricating oil comprising a mineral lubricating oil containingdissolved a small amount of an oil-soluble polyvalent metal salt of analpha amino fatty acid having at least 16 carbon atoms and not more thanone olefinic double bond, and having attached to the amino group atleast one hydrocarbon radical.

9. Lubricating oil comprising a mineral lubricating oil containingdissolved a small amount of an oil-soluble polyvalent metal salt of analpha amino naphthenic acid having attached to the amino group at leastone hydrocarbon radical said salt being further characterized by beingresistant to oxidation under normal lubricating conditions in internalcombustionengines.

l0. Lubricating oil comprising a mineral lubricating oil containingdissolved a small amount of an oil-soluble polyvalent salt of an alphaamino parafiin wax monocarboxylic acid having attached to the aminogroup at least one hydrocarbon radical said salt being furthercharacterized by being resistant to oxidation under normal lubricatingconditions in internal combustion engines.

11. Lubricating oil comprising a mineral lubricating oil containingdissolved a small amount ofcalcium alpha piperidino stearate.

ELLIS R. WHITE.

